In various multistage turbomachines used for energy conversion, such as turbines, a fluid is used to produce rotational motion. In a gas turbine engine, for example, air is compressed through successive stages in a compressor and mixed with fuel in a combustor. The combination of air and fuel is then ignited for generating combustion or hot working gases that are directed to turbine stages to produce the rotational motion. The compressor stages and turbine stages typically have stationary or non-rotary components, e.g., vane structures, that cooperate with rotatable components, e.g., rotor blades, for compressing air and expanding the hot working gases.
The inaccessibility and small size of the open space within the combustion turbine, and between and among the turbine blades, makes inspection of the blades difficult without partial disassembly of the turbine. In-situ inspections can be performed using a borescope or a camera system. Inspection systems using a camera provide images that can be difficult to analyze in that images provided by cameras, such as cameras that utilize CCD imaging matrices, are strongly dependent on the level of contrast between adjacent features being imaged to visualize details of a viewed object. Hence, in the low light environment typically available for in-situ inspection of turbine blades, where it is difficult to provide adequate illumination, conventional camera imaging of the turbine blades may be limited in relation to providing identification of details of interest, such as defects, forming on the turbine blades.